1. Field of the Invention
The invention relates to a valve device and, more particularly, to a valve device, such as a manual valve for a gas tank that stores high-pressure gas such as hydrogen gas, that is able to open or shut off a flow passage in which a pressure difference is large.
2. Description of the Related Art
A valve device is provided for a plug element for closing an opening of a gas tank. The valve device has one or more flow passages that provide fluid communication between the inside and outside of the gas tank. The valve device controls flow of gas in the one or more flow passages. An example of the valve device includes a manual valve that is manually opened or closed, which is, for example, described in Japanese Patent Application Publication No. 2006-144841 (JP-A-2006-144841).
The manual valve described in JP-A-2006-144841 is arranged in a first recess (21) that is open to an outer face (16a) of a plug element housing (16) as shown in FIG. 3 of JP-A-2006-144841. The manual valve (14) includes a housing (35), a valve element (36) and an operating screw (37). The housing (35) has a cylindrical shape with a bottom portion (35a) formed at one end. The valve element (36) is accommodated in the housing (35) so that the valve element (36) is slidable in the axial direction. The operating screw (37) is used to operate the valve element (36). The housing (35) is arranged in the first recess (21) so that the bottom portion (35a) contacts a lid element (26) of a check valve (9). Then, the bottom portion (35a) of the housing (35) has a through-hole (38) that is in fluid communication with a through-hole (32) of the check valve (9). A side wall (35b) near the bottom portion (35a) has a through-hole (39) that is in fluid communication with a first flow passage (18). Then, an O ring (36c), which serves as a seal member, is fitted on the outer periphery of the valve element (36). A distal end portion (36a) of the valve element (36) has a conical shape, and contacts or moves away from a valve seat (40).
FIG. 5 and FIG. 6 show a manual valve according to another related art. The manual valve includes a valve housing 91, a seal member 93 and a stem 92. The valve housing 91 defines a cylindrical space 99 having a cylindrical shape with a bottom portion at one end. The seal member 93 is able to contact or move away from a valve seat 991. The valve seat 991 has a flow passage opening 911a (one end of a first communication hole 911), and is provided at the bottom portion of the cylindrical space 99. The stem 92 holds the seal member 93 fitted at one end of the stem 92. The seal member 93 contacts or moves away from the valve seat 991 to thereby close or open the valve. The seal member 93 may be made of a material different from that of the stem 92, or the like. When the seal member 93 is, for example, made of a resin material, the seal member 93 is able to closely contact the valve seat 991, and it is possible to provide a manual valve having a high sealing performance.
Incidentally, when the seal member is provided, close contact property with the valve seat improves and, as a result, the performance of the valve device improves. However, when the valve seat 991 side with respect to the seal member is connected to a low-pressure side and a cylindrical space 99 side with respect to the seal member is connected to a high-pressure side, the seal member 93 may adhere to the low-pressure side valve seat 991 because of its high sealing performance and may interfere with opening and closing of the valve thereafter.